Coaxial Ignition Device Shear Layer Resonance
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Solution Overview
Problem
Existing ignition devices for rocket engines rely on convergent nozzles to generate under-expanded supersonic jets, which are sensitive to boundary conditions and lack robustness, leading to inconsistent and delayed ignition.
Innovation Solution
An ignition device utilizing a coaxial injector with convergent-divergent nozzles to inject fluids with different velocities, generating strong shear layers and pressure oscillations within a resonator cavity, converting fluid flow energy into heat for reliable ignition without external energy or moving parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If convergent nozzles are used to generate under-expanded supersonic jets, then ignition can be achieved, but the system lacks robustness and shows strong dependence on boundary conditions
Solution Approach 1:
The patent changes the nozzle geometry from convergent to convergent-divergent (Laval nozzle) configuration, which fundamentally alters the flow characteristics. This parameter change enables the generation of supersonic jets with different expansion properties that are less sensitive to boundary conditions, thereby improving ignition reliability while reducing boundary condition sensitivity
Solution Approach 2:
The patent introduces dynamic flow control by using adjustable guide vanes that can modify the flow direction and characteristics in real-time. This dynamic adjustment capability allows the system to adapt to varying boundary conditions, maintaining robust ignition performance across different operating scenarios
2Power
If multiple fluid flows with different velocities are injected into the ignition chamber, then stronger shear layers and pressure oscillations are generated, but the device complexity increases
Solution Approach 1:
The patent combines multiple fluid injection functions into a single coaxial injector assembly. The inner and outer nozzles are integrated into one structure, with the inner nozzle injecting one fluid and the outer nozzle injecting another fluid. This merging approach generates the required multiple velocity streams and strong shear layers while avoiding the complexity of separate injection systems
Solution Approach 2:
The patent utilizes pneumatic principles by designing the coaxial injector to generate supersonic flows through pressure differential control. The system uses gas dynamics and fluid mechanics to create the desired flow patterns without mechanical moving parts, reducing device complexity while maintaining high ignition power
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves faster and more reliable ignition with reduced heat loss, suitable for long-term, maintenance-free operation in satellite propulsion and other applications, by focusing pressure oscillations to concentrate heat and minimize convection, thereby enhancing the robustness and efficiency of the ignition process.
Implementation Method 1
Recent studies, however, show that also strong shear layers are able to excite oscillations within resonator cavities
Implementation Method 2
converting fluid flow energy into heat for reliable ignition without external energy or moving parts
Implementation Method 3
strong thermal effects may be observed. As a driving factor, natural instabilities within the open jet—barrel shocks—are identified, which induce shockwaves within the resonator
Implementation Method 4
induce shockwaves within the resonator
Implementation Method 5
strong thermal effects may be observed
Implementation Method 6
focusing pressure oscillations to concentrate heat and minimize convection
Data Source
AI summary
An igniting device for igniting a mixture, in particular for an engine, comprises an energy converting device and a fluid flow injecting device. The energy converting device is configured for converting fluid flow energy of at least one fluid flow into heat, thereby igniting the mixture. The energy converting device comprises an ignition chamber for the at least one fluid flow. The fluid injecting device is configured for injecting a plurality of fluid flows into the ignition chamber. The injection takes place such that a first fluid flow is injected into the ignition chamber with a higher fluid flow velocity than a second fluid flow.